Rubber gloves are widely utilized for home use, industrial use such as food industry and electronic device manufacturing, and medical use. It is required for rubber gloves to have various characteristics such that it should stretch by weaker force following movement of fingers so that hands do not become tired upon prolonged wearing (i.e., wearing comfort) and that it should not be broken during operation (i.e., sufficient tensile strength).
Further, particularly for thin rubber gloves, there has been sometimes a problem that crack occurs in crotch of fingers when one continues operation moving fingers with wearing them (i.e., low resistance to flexing fatigue).
Conventionally, as rubber gloves having high tensile strength and excellent oil resistance, there are often used those obtained by dip-forming of a dip-forming composition comprising carboxylated acrylonitrile-butadiene copolymer latex, sulfur and a curing accelerator.
For example, Patent document 1 discloses a dip-formed rubber glove from a dip-forming composition comprising a carboxylated acrylonitrile-butadiene rubber latex, zinc oxide, sulfur and a curing accelerator. Such a glove is very comfortable for wearing, but has poor tensile strength. So it is easy to be broken during wearing.
Further, Patent document 2 discloses a dip-formed glove from a dip-forming composition comprising a carboxylated acrylonitrile-butadiene copolymer latex, sulfur and a curing accelerator but not zinc oxide. Such a glove has high tensile strength, which reduces risk of breakage during wearing, but it is uncomfortable for wearing.
Further, Patent document 3 discloses a dip-formed rubber glove from a dip-forming composition comprising an acrylonitrile-butadiene copolymer latex containing a specific amount of carboxyl groups, a small amount of zinc oxide, a relatively large amount of sulfur and a curing accelerator. However, when one continues operation for a long time with wearing it, such a glove itself sometimes suffers coloration, which significantly lowers its commercial value.
In addition, the above-mentioned rubber glove manufactured by dip-forming of a dip-forming composition comprising sulfur and a curing accelerator as essential components, although relatively excellent in resistance to flexing fatigue, sometimes suffers coloration when one continues operation for a long time with wearing it, which significantly lowers its commercial value.
On the other hand, there has been also studied manufacturing of a dip-formed article where an organic peroxide is used as a crosslinker without using sulfur and a curing accelerator.
For example, Patent document 4 discloses a dip-formed article obtained by dip-forming of a dip-forming composition comprising a natural or synthetic rubber latex formulated with an organic peroxide such as dicumyl peroxide or di-t-butyl peroxide followed by crosslinking at a considerably high temperature in chemically inactive melted salt bath. However, such a rubber glove, although it has wearing comfort and sufficient tensile strength, has problems of coloration due to exposure to a high temperature during production and of low resistance to flexing fatigue causing crack in crotch of fingers in use for 2-3 hr.
Patent document 1: U.S. Pat. No. 5,014,362
Patent document 2: WO 97/48765
Patent document 3: WO 00/21451
Patent document 4: WO 01/77210